<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python documentation Index' />
<link rel="first" href="lib.html" title='Python library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="module-gdbm.html" />
<link rel="prev" href="module-whichdb.html" />
<link rel="parent" href="persistence.html" />
<link rel="next" href="module-gdbm.html" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name='aesop' content='information' />
<title>13.8 dbm -- Simple ``database'' interface</title>
</head>
<body>
<div class="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="13.7 whichdb  "
  href="module-whichdb.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="13. data Persistence"
  href="persistence.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="13.9 gdbm  "
  href="module-gdbm.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="module-whichdb.html">13.7 whichdb  </a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="persistence.html">13. Data Persistence</a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="module-gdbm.html">13.9 gdbm  </a>
</div>
<hr /></div>
</div>
<!--End of Navigation Panel-->

<h1><a name="SECTION0015800000000000000000">
13.8 <tt class="module">dbm</tt> --
         Simple ``database'' interface</a>
</h1>

<p>
<a name="module-dbm"></a>  
<p class="availability">Availability: <span
 class="platform">Unix</span>.</p>

<p>
The <tt class="module">dbm</tt> module provides an interface to the <span class="Unix">Unix</span>
(<code>n</code>)<code>dbm</code> library.  Dbm objects behave like mappings
(dictionaries), except that keys and values are always strings.
Printing a dbm object doesn't print the keys and values, and the
<tt class="method">items()</tt> and <tt class="method">values()</tt> methods are not supported.

<p>
This module can be used with the ``classic'' ndbm interface, the BSD
DB compatibility interface, or the GNU GDBM compatibility interface.
On <span class="Unix">Unix</span>, the <b class="program">configure</b> script will attempt to locate the
appropriate header file to simplify building this module.

<p>
The module defines the following:

<p>
<dl><dt><b><span class="typelabel">exception</span>&nbsp;<tt id='l2h-2513' xml:id='l2h-2513' class="exception">error</tt></b></dt>
<dd>
Raised on dbm-specific errors, such as I/O errors.
<tt class="exception">KeyError</tt> is raised for general mapping errors like
specifying an incorrect key.
</dd></dl>

<p>
<dl><dt><b><tt id='l2h-2514' xml:id='l2h-2514'>library</tt></b></dt>
<dd>
Name of the <code>ndbm</code> implementation library used.
</dd></dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2515' xml:id='l2h-2515' class="function">open</tt></b>(</nobr></td>
  <td><var>filename</var><big>[</big><var>, flag</var><big>[</big><var>, mode</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
Open a dbm database and return a dbm object.  The <var>filename</var>
argument is the name of the database file (without the <span class="file">.dir</span> or
<span class="file">.pag</span> extensions; note that the BSD DB implementation of the
interface will append the extension <span class="file">.db</span> and only create one
file).

<p>
The optional <var>flag</var> argument must be one of these values:

<p>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="center">Value</th>
      <th class="left"  >Meaning</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="center" valign="baseline"><code>'r'</code></td>
        <td class="left"  >Open existing database for reading only (default)</td></tr>
    <tr><td class="center" valign="baseline"><code>'w'</code></td>
        <td class="left"  >Open existing database for reading and writing</td></tr>
    <tr><td class="center" valign="baseline"><code>'c'</code></td>
        <td class="left"  >Open database for reading and writing, creating it if
               it doesn't exist</td></tr>
    <tr><td class="center" valign="baseline"><code>'n'</code></td>
        <td class="left"  >Always create a new, empty database, open for reading
               and writing</td></tr></tbody>
</table></div>

<p>
The optional <var>mode</var> argument is the <span class="Unix">Unix</span> mode of the file, used
only when the database has to be created.  It defaults to octal
<code>0666</code>.
</dl>

<p>
<div class="seealso">
  <p class="heading">See Also:</p>

  <dl compact="compact" class="seemodule">
    <dt>Module <b><tt class="module"><a href="module-anydbm.html">anydbm</a></tt>:</b>
    <dd>Generic interface to <code>dbm</code>-style databases.
  </dl>
  <dl compact="compact" class="seemodule">
    <dt>Module <b><tt class="module"><a href="module-gdbm.html">gdbm</a></tt>:</b>
    <dd>Similar interface to the GNU GDBM library.
  </dl>
  <dl compact="compact" class="seemodule">
    <dt>Module <b><tt class="module"><a href="module-whichdb.html">whichdb</a></tt>:</b>
    <dd>Utility module used to determine the type of an
                      existing database.
  </dl>
</div>

<div class="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="13.7 whichdb  "
  href="module-whichdb.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="13. data Persistence"
  href="persistence.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="13.9 gdbm  "
  href="module-gdbm.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="module-whichdb.html">13.7 whichdb  </a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="persistence.html">13. Data Persistence</a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="module-gdbm.html">13.9 gdbm  </a>
</div>
</div>
<hr />
<span class="release-info">Release 2.5.1, documentation updated on 18th April, 2007.</span>
</div>
<!--End of Navigation Panel-->
<address>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</address>
</body>
</html>
